The effect of HIV, behavioural change, and STD syndromic management on STD epidemiology in sub-Saharan Africa: simulations of Uganda

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Background:Herpes simplex virus type 2 (HSV-2) infection increases acquisition and transmission of HIV, but the results of trials measuring the impact of HSV-2 therapy on HIV genital shedding and HIV acquisition are mixed, and the potential impact of HSV-2 therapy on the incidence of HIV at the population level is unknown.Methods:The effects of episodic and suppressive HSV-2 therapy were simulated using the individual-level model STDSIM fitted to data from Cotonou, Benin (relatively low HIV prevalence) and Kisumu, Kenya (high HIV prevalence). Clinician- and patient-initiated episodic therapy, started when symptomatic, were assumed to reduce ulcer duration. Suppressive therapy, given regardless of symptoms, was also assumed to reduce ulcer frequency and HSV-2 infectiousness.Results:Clinician-initiated episodic therapy in the general population had almost no effect on the incidence of HIV. The impact of patient-initiated therapy was higher because of earlier treatment initiation, but still low (<5%) unless symptom recognition and treatment-seeking behaviour were very high. Suppressive therapy given to female sex workers (FSW) in Kisumu had little effect on population HIV incidence. In Cotonou, suppressive therapy in FSW with high coverage and long duration reduced population HIV incidence by >20% in the long term. Impact was increased in both cities by also treating a proportion of their clients. Long-term suppressive therapy with high coverage in the general population could reduce HIV incidence by more than 30%.Conclusions:These results show that HSV-2 therapy could potentially have a population-level impact on the incidence of HIV, especially in more concentrated epidemics. However, a substantial impact requires high coverage and long duration therapy, or very high symptom recognition and treatment-seeking behaviour.

Section: Methodsmentioning

confidence: 99%

Population-level effect of HSV-2 therapy on the incidence of HIV in sub-Saharan Africa

White

Freeman

Orroth

et al. 2008

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“…Hence the population adjustment must take into account the proportion sexually active in the different age strata in the sampled group (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29) year olds). Diagnostic adjustments were applied to the observed prevalence in each age group.…”

Section: Estimation Of Selection Biasmentioning

confidence: 99%

Comparison of STD prevalences in the Mwanza, Rakai, and Masaka trial populations: the role of selection bias and diagnostic errors

Orroth

Korenromp

White

et al. 2003

Objectives: To assess bias in estimates of STD prevalence in population based surveys resulting from diagnostic error and selection bias. To evaluate the effects of such biases on STD prevalence estimates from three community randomised trials of STD treatment for HIV prevention in Masaka and Rakai, Uganda and Mwanza, Tanzania. Methods: Age and sex stratified prevalences of gonorrhoea, chlamydia, syphilis, HSV-2 infection, and trichomoniasis observed at baseline in the three trials were adjusted for sensitivity and specificity of diagnostic tests and for sample selection criteria. Results: STD prevalences were underestimated in all three populations because of diagnostic errors and selection bias. After adjustment, gonorrhoea prevalence was higher in men and women in Mwanza (2.8% and 2.3%) compared to Rakai (1.1% and 1.9%) and Masaka (0.9% and 1.8%). Chlamydia prevalence was higher in women in Mwanza (13.0%) compared to Rakai (3.2%) and Masaka (1.6%) but similar in men (2.3% in Mwanza, 2.7% in Rakai, and 2.2% in Masaka). Prevalence of trichomoniasis was higher in women in Mwanza compared to women in Rakai (41.9% versus 30.8%). Herpes simplex virus type 2 (HSV-2) seroprevalence and prevalence of serological syphilis (TPHA+/RPR+) were similar in the three populations but the prevalence of high titre syphilis (TPHA+/RPR >1:8) in men and women was higher in Mwanza (5.6% and 6.3%) than in Rakai (2.3% and 1.4%) and Masaka (1.2% and 0.7%). Conclusions: Limited sensitivity of diagnostic and screening tests led to underestimation of STD prevalence in all three trials but especially in Mwanza. Adjusted prevalences of curable STD were higher in Mwanza than in Rakai and Masaka. P revalences of sexually transmitted diseases (STD) are often compared between populations in order to gain a better understanding of STD and HIV epidemiology or to determine which control strategy may be most effective in a given epidemiological situation. Three community randomised trials of STD treatment as HIV prevention strategies have been conducted in east Africa in Mwanza, Tanzania, and Masaka and Rakai, Uganda.1-3 In the Mwanza trial, improved STD case management was associated with a 38% reduction in HIV incidence. 4 In contrast, in Uganda a trial of information, education, and communication coupled with improved STD case management had no impact on HIV incidence in Masaka district 5 and STD mass treatment had no impact on HIV incidence in Rakai district.3 Baseline prevalence of gonorrhoea and chlamydia was about 5% or less in the populations while that for serological syphilis was 10-15%. Various hypotheses have been suggested to explain the apparently contrasting results, including that the Mwanza and Rakai trials differed with respect to the stage of the HIV epidemic, that the proportion of ulcers due to herpes simplex virus type 2 (HSV-2) was higher in Rakai than Mwanza, and that differences in the interventions-that is, continuous treatment of symptomatic STD (as in Mwanza) may have a larger effect than treating all STD periodically (a...

“…This suggests that HSV-2 was already widespread in Africa before the HIV epidemic, and that HIV infection is not an important determinant of the HSV-2 prevalence in the population. This conclusion is also supported by mathematical modelling of the Ugandan HIV epidemic, in which stable HSV-2 prevalence was attributed to the small increase due to enhanced transmission by HIV being balanced by the effects of HIV-related mortality,18 and by modelling of the interaction of HIV and HSV-2 in Kisumu, Kenya 19…”

Section: Discussionmentioning

confidence: 74%

Herpes simplex virus type 2 trends in relation to the HIV epidemic in northern Malawi

Glynn

Crampin

Ngwira

et al. 2008

Objectives:It is unclear whether the high prevalence of herpes simplex virus type 2 (HSV-2) found in much of Africa predates the HIV epidemic or is, to some extent, a consequence of it. HSV-2 prevalence trends in a rural African community were assessed over a period in which HIV prevalence rose sharply, and antenatal clinic (ANC) surveillance was explored as a method of estimating community HSV-2 prevalence.Methods:HSV-2 seroprevalence was determined among community controls seen for case–control studies of mycobacterial disease in Karonga district, Malawi, in 1988–90, 1998–2001 and 2002–5, and in women attending ANC as part of surveillance for HIV in 1999–2000. Over this period HIV prevalence rose from 4% to 12%.Results:HSV-2 prevalence in all periods increased sharply with age and was higher in women than in men. After excluding migrants, there was no evidence of change in HSV-2 prevalence in the different periods. Women in the ANC group had lower HSV-2 prevalence than those in the community, but the ANC prevalence was a good approximation to the combined male and female prevalence for the same age group.Conclusions:This study suggests that HSV-2 was already widespread before the HIV epidemic and has not been greatly influenced by it. It also demonstrates that ANC surveillance may be useful for estimating community HSV-2 prevalence.